1. Field of the Invention
The present invention relates to a picture size selective camera, and more particularly, a picture size selective camera permitting photography in a photography mode of a normal size and a photography mode of a picture size different from the normal size.
2. Description of the Related Art
In recent years, numerous proposals have been made for a camera permitting photography of a normal size as well as photography of a trimming size such as a pseudo-panorama size (for example, a picture size of 13 mm by 36 mm, hereinafter, a panorama size). Such cameras have already been put on the market. As for the camera permitting panoramic photography, a proposal has been made for a camera in which a picture range of a panorama size can be identified In the field of view of the viewfinder. For example, Japanese Patent Laid-open No. 61-285432 has disclosed a technological means that, when panorama photography is designated, as shown in FIG. 9, shields the upper and lower parts of the field of view in a viewfinder with opaque masks and thus enables identification of a picture range of a panorama size. Japanese Patent Laid-open 62-50741 has introduced an example in which various field frames that indicate picture ranges for photography of a trimming size are installed in a viewfinder.
Using the technological means proposed in the Japanese Patent Laid-open No. 61-285432, the entire field of view except a picture range of a panorama size is masked as shown in FIG. 9. In a panoramic photography mode of a panorama size in which a narrow range alone especially looks small, or in a pseudo-telephotography mode of a pseudo-telephotographic size, a photographer has difficulties in achieving framing appropriately while looking around.
The technological means proposed in the Japanese Patent Laid-open No. 62-50741 facilitates misidentification of a photography mode because of the existence of various kinds of frames.
According to the technological means proposed in Japanese Patent Laid-open No. 61-295534, a ray control unit is installed in an exposure control unit for a photographic camera permitting pseudo-telephotography. The ray control unit includes a viewfinder and selects a field of view for pseudo-telephotography so that a quantity of light reaching a sensitized element will be controlled in proportion to a quantity of light supplied to the pseudo-telephotographic field of view. The beam control unit shields a focusing screen with opaque (dark) masks without changing the angle of light reception of a photometric element (sensitized element), and thus indicates a picture range that is narrower than a normal size. Photometry is then carried out.
The Japanese Patent Laid-open No. 61-295534 has further disclosed a technological means that uses an LCD to display a field frame for defining a trimming picture range.
U.S. Pat. No. 4,943,825 has proposed a technological means wherein, whichever photography mode is selected, photomerry involves a certain range alone that substantially corresponds to the picture range for a photography mode of a pseudo-telephotographic size, so that an exposure value can be calculated correctly.
U.S. Pat. No. 4,774,536 has proposed a technological means that includes a first photomerry means and a second photomerry means, and selects either of these two photomerry means depending on a photography mode.
However, the ray control unit disclosed in the Japanese Patent Laid-open No. 61-295534 indicates a picture range, which is narrower than the normal picture range, by shielding the focusing screen with opaque (dark) masks without modifying the angle of light reception of a photometric element (sensitized element), and then performs photomerry. Photomerry concludes that the areas of the opaque (dark) masks are dark. As a whole, the focusing screen is likely to be recognized as darker than it actually is.
In the Japanese Patent Laid-open No. 61-295534, the field frame representing the trimming picture range is displayed on an LCD. The incorporation of the LCD results in a cost increase. Since the LCD is always conducting during the display of a field frame, a large amount of power is required. If the surroundings are dark, it is hard to look at the LCD. Since the LCD intercepts light, the viewfinder becomes dark.
In the photometric means in the U.S. Pat. No. 4,943,825, photomerry is oriented to the picture range of a pseudo-telephotographic size; that is, a considerably narrow picture size for, for example, panoramic photography (the long side of film has a normal dimension but the short side thereof is a half of a normal dimension). For photography of a normal picture size, there is a problem that photomerry is oriented to the center of the picture range but not performed uniformly over the picture range.
The photomerry means in the U.S. Pat. No. 4,774,536 consists of two photomerry means, which results in a complex photomerry unit.
U.S. Pat. Re. No. 32,797 has proposed a technological means in which a photomerry means performs photomerry on a trimming picture range for trimming photography, and then an exposure control means performs parameter compensation on the metered value to calculate a correct exposure value.
The technological means in the U.S. Pat. Re. No. 32,797 has a drawback that the luminance limit for photomerry of low luminance decreases because of the narrow photometric range for trimming photography.
The U.S. Pat. No. 4,774,536 has proposed a technological means that comprises photomerry means for performing photomerry on wide and narrow ranges respectively and that forcibly activates the means for performing photomerry on a narrow range in the photography mode of a pseudo-telephotographic size (mode in which only a narrow picture range is printed and enlarged). The U.S. Pat. No. 4,943,825 has disclosed a technological means that includes a means for performing photomerry on a predetermined range regardless of a photography mode. The photometric range is substantially equal to or narrower than a picture range In the photography mode of a pseudo-telephotographic size.
Problems concerning the related arts disclosed in the U.S. Pat. Nos. 4,774,536 and 4,943,825 will be discussed below.
FIG. 42 is an explanatory diagram showing the distribution of sensitivity of a photomerry unit with respect to incident rays entering through a focusing screen in a conventional picture size selective camera. In FIG. 42, each contour line indicated with reference numeral 201 links points of the same sensitivity. A contour line indicates a sensitivity that is twice or half the sensitivity of an adjoining line.
When the generally-employed photometric sensitivity distribution as that shown in FIG. 42 is employed for a picture size selective camera, a metered value has an error. The underlying reason will be described below.
FIG. 43 is an explanatory diagram showing the distribution of sensitivity of a photomerry unit in a conventional picture size selective camera occurring when masks are applied to the field of view in the viewfinder to restrict the focusing screen to a panorama size.
In general, a photomerry unit is controlled so that it will provide a normal value when viewfinder field masks 202 are not present. In this example, when the viewfinder field masks 202 are inserted to provide a selected panorama size, rays originating from the hatched areas in the right of FIG. 43 are suppressed and are not sensed at all. Photomerry therefore concludes that the areas are dark. In other words, the areas are recognized as darker than they actually are. In an automatic exposure mode, a larger exposure value is therefore specified. Overexposure ensues.
FIG. 44 is an explanatory diagram showing the photometric sensitivity distribution of the technological means proposed in the U.S. Pat. No. 4,943,825. In this example, photomerry is confined to a minimum selective picture range.
According to the above method, a photometric error does not occur in the photography mode of a trimming size. However, as shown in FIG. 44, since photomerry is concentrated on the center area alone, a photograph with a well-balanced quantity of light is unavailable in the normal photography mode because quantities of light in the surrounding areas are not taken into account. As shown in FIG. 44, assuming that the light of a room lamp or the like is seen present in the upper part of a film screen, the light is ignored completely. When the whole film screen is used for printing, an area surrounding the room lamp results in marked overexposure. Although the center of the film screen is properly exposed, the film screen results in an unnatural photograph as a whole.